The cells in our bodies are far outnumbered by the microbes which also take up residence there, but these organisms are beneficial to us in many ways. For example, we rely on beneficial bacteria to fortify our immune systems and aid in the breakdown and absorption of food particles in the gut. Scientists have recently discovered that the microbes which are found throughout our bodies also play a vital role in keeping the blood-brain barrier intact.

The Blood-Brain Barrier

The blood-brain barrier is a vital physical blockade which prevents harmful chemicals and pathogens from passing into the brain. Scientists in Stockholm discovered that the blood-brain barrier relies on the presence of gap junction proteins, which are similar to the gap junction proteins which are important for building the intestinal wall. They tested the integrity of the blood-brain barrier in developing and adult mice by raising mice in a sterile environment to ensure that they were germ-free.

The scientists then injected antibodies (which are too large to pass through the blood-brain barrier) into embryos developing within germ-free mothers, as well as embryos developing within mothers who harbored normal germs. While the embryos from the normal germ-containing mothers had intact blood-brain barriers which formed a tight seal by day 17 of development, the embryos which developed in germ-free mothers displayed antibodies in their brains, proving that the blood-brain barrier had not formed properly. The embryos from germ-free mothers also had far fewer intact gap junction proteins in the blood-brain barrier.

Microbes and Multiple Sclerosis

These findings suggest that microbes are essential for normal development of the blood-brain barrier. If antibiotics, or food items which have antibiotics, are taken while a woman is pregnant, they could result in defective blood-brain barrier formation in the child. Further research into the link between microbes and normal blood-brain barrier development could lead to possible cures for diseases such as multiple sclerosis, which involves unexplained mechanisms that make the brain more vulnerable to damage.